Maths Questions

[quik5i1ver]

Er yeah, we're all waiting....................

Wait over..
Click Here if maths scares you :lol:

 

[quik5i1ver]

Trying to remember how to solve such problems... do I need to use calculus?! If only I had my maths books to hand!!!

 

[quik5i1ver]

I've worked out 2 expressions, one for h and one for r.

h = 2500/(pi)r^2
r = (2500/(pi)h)^1/2

From here I can't remember how to find the minimum values..

 

[BenG]

A = 2(pi)r h + (pi) r^2

You need to substitute h into the fromula for A. Then use differentiation to work out r

 

[BenG]

A = 2(pi)r (2500/(pi)r^2) + (pi)r^2
= 5000/r + (Pi)r^2
= 5000 r^-1 + (Pi)r^2

(DA/DR) = -5000 r^-2 + 2(Pi)r = 0 for min/max
(-5000/r^2) + 2(pi)r = 0
-5000 + 2(pi)r^3
2(pi)r^3 = 5000
r^3 = (5000/2(pi))

r = 3((square root) 5000/2(pi)) = 9.27cm
h = 2500/pi(9.27)^2 = 9.27cm

 

[hoolio]

A = 2(pi)r (2500/(pi)r^2) + (pi)r^2
= 5000/r + (Pi)r^2
= 5000 r^-1 + (Pi)r^2

(DA/DR) = -5000 r^-2 + 2(Pi)r = 0 for min/max
(-5000/r^2) + 2(pi)r = 0
-5000 + 2(pi)r^3
2(pi)r^3 = 5000
r^3 = (5000/2(pi))

r = 3((square root) 5000/2(pi)) = 9.27cm
h = 2500/pi(9.27)^2 = 9.27cm

Cue i think we've got a glitch on the forum, it seems to be translating everything into gobbledegook :?

 

[nickboazracing]

:shock:

Er..
It's amazing how much you forget when you're not puting something into practice on a reguler basis. I used to quite enjoy maths stuff like that but now I haven't got a clue!

 

[Cue]

A = 2(pi)r (2500/(pi)r^2) + (pi)r^2
= 5000/r + (Pi)r^2
= 5000 r^-1 + (Pi)r^2

(DA/DR) = -5000 r^-2 + 2(Pi)r = 0 for min/max
(-5000/r^2) + 2(pi)r = 0
-5000 + 2(pi)r^3
2(pi)r^3 = 5000
r^3 = (5000/2(pi))

r = 3((square root) 5000/2(pi)) = 9.27cm
h = 2500/pi(9.27)^2 = 9.27cm

Cue i think we've got a glitch on the forum, it seems to be translating everything into gobbledegook :?

yeh i thought it had gone into php mode again...

 

[quik5i1ver]

Ok so a slightly simpler question

For the following is a number sequence:
1,2,6,42,1806,...

a) Form an equation in terms of n to represent this sequence
b) Provide the next number in the sequene

 

[SharkyUK]

Ok so a slightly simpler question

For the following is a number sequence:
1,2,6,42,1806,...

a) Form an equation in terms of n to represent this sequence
b) Provide the next number in the sequene

n * (n + 1) => 3263442

 

[BenG]

n (squared) + n

3263442